Fueling & Injection Fuel Pumps | Injectors | Rails | Regulators | Tanks

7 LB pressure drop normal?

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Old Nov 13, 2006 | 02:48 PM
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Default 7 LB pressure drop normal?

Hello everyone,

I just finished putting in my fuel filter and I let the car heat up and ran it to make sure that there were no leaks and stuff. I did notice that for awhile now (pre new fuel filter) that I was losing roughly 6-7LBS of fuel pressure at WOT. Is this a problem, and if so, is a fuel pump the next on the list? I've heard that the pumps on these cars are fairly weak.
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Old Nov 13, 2006 | 04:11 PM
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I get the same pressure drop on my bolt-ons only car...it is about a 6 psi drop at WOT for me. Annoying, and it wasn't my fuel filter. A new fuel pump is on my list...but it isn't a concern because this one isn't shot - I just don't think it can supply the volume of fuel needed.
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Old Nov 13, 2006 | 07:19 PM
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I think it is fairly normal for a drop such as this, but I think a new fuel pump would be a good idea on a 7 year old car.
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Old Nov 14, 2006 | 12:20 PM
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Originally Posted by Ragingwolf51
I think it is fairly normal for a drop such as this, but I think a new fuel pump would be a good idea on a 7 year old car.
From what I've gathered, yes...I'm not worried about mine at all, simply due to its repeatability. It hasn't affected my tune's stability, so that's all that matters to me.
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Old Nov 14, 2006 | 12:57 PM
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Works for me. Thanks a lot.
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Old Nov 14, 2006 | 01:33 PM
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Even with a perfect pump and filter, you have 10 feet or
so of skinny tube to blow that gasoline through at full flow,
and pressure is set at the back, not the point of use. So
you're stuck with a significant flow/pressure drop which
only gets worse as you increase fuel demand (airflow,
injectors).

A rail mounted, return style regulator is the ideal but needs
a bit of replumbing and expensive parts. Though I've had
the notion for a while now, that maybe it could all be done
using the in-tank regulator and just replacing the feed with
fatter forward tubing and using the old feed for a return. If
only there was a "kit". good to go. More forward cross section
would stretch the limits of the stock pump a fair bit IMO.
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Old Nov 14, 2006 | 03:34 PM
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From: Dayton, OH
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Originally Posted by jimmyblue
Even with a perfect pump and filter, you have 10 feet or
so of skinny tube to blow that gasoline through at full flow,
and pressure is set at the back, not the point of use. So
you're stuck with a significant flow/pressure drop which
only gets worse as you increase fuel demand (airflow,
injectors).

A rail mounted, return style regulator is the ideal but needs
a bit of replumbing and expensive parts. Though I've had
the notion for a while now, that maybe it could all be done
using the in-tank regulator and just replacing the feed with
fatter forward tubing and using the old feed for a return. If
only there was a "kit". good to go. More forward cross section
would stretch the limits of the stock pump a fair bit IMO.
Speaking of a "kit"...what ever happened to the Racetronix fuel rail mounted PnP regulator? It is still on their website, but was supposed to be out in 2005.
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